Method for Operating an Automatic Transmission of a Hybrid Vehicle, Automatic Transmission and Hybrid Vehicle

Abstract

A method for operating an automatic transmission of a hybrid vehicle which has an electric traction machine and an internal combustion engine. A drag torque is provided at the electric traction machine. On the basis of a maximally available electric power for driving the electric traction machine, a characteristic map having respective curves for respective gears of the automatic transmission of the hybrid vehicle is created. The characteristic map is adjusted according to the drag torque to be provided by each curve being reduced by the drag torque to be provided. A shifting logic is specified in which respective shifting points for shifting the automatic transmission are defined at intersections of the curves of adjacent gears of the adjusted characteristic map, wherein the automatic transmission is shifted on the basis of the shifting logic in the respective shifting points.

Claims

1-10. (canceled)

11. A method for operating an automatic transmission of a hybrid vehicle which has an electric traction machine and an internal combustion engine, the electric traction machine being configured to provide traction power output for the hybrid vehicle and to crank over the internal combustion engine, wherein a drag torque provided at the electric traction machine is required to crank over the internal combustion engine, the method comprising: producing a characteristic diagram for the electric traction machine, starting from a maximum available electrical power output for driving the electric traction machine, with respective curves for respective gears of the automatic transmission of the hybrid vehicle, the curves formed by plotting a torque against a rotational speed, and the characteristic diagram being adapted in a manner which is dependent on the drag torque to be provided, by each curve being reduced by the drag torque to be provided; and, predefining a shifting logic, in which respective shift points for shifting the automatic transmission are defined at points of intersection of the curves of adjacent gears of the adapted characteristic diagram; and, shifting the automatic transmission at the respective shift points using the shifting logic.

12. The method according to claim 11, wherein: the maximum available power output for the electric traction machine is determined in a manner which is dependent on an available power output which is provided by way of a battery.

13. The method according to claim 12, wherein: the available power output which is provided by the battery is determined in a manner which is dependent on a charging state of the battery and/or a temperature of the battery.

14. The method according to claim 11, wherein: the method is carried out during a journey of the hybrid vehicle.

15. The method according to claim 11, wherein: in the case of the respective curves in the characteristic diagram, the torque is plotted against a transmission output speed, and the automatic transmission is shifted on the basis of the transmission output speed.

16. The method according to claim 11, wherein: the drag torque to be provided is determined in a manner which is dependent on a cut-off position of a piston of the internal combustion engine.

17. The method according to claim 11, wherein: the drag torque to be provided is determined in a manner which is dependent on a temperature of the internal combustion engine.

18. The method according to claim 11, wherein: the drag torque to be provided is determined in a manner which is dependent on a variable of the internal combustion engine.

19. The method according to claim 11, wherein: for a switchover between the electric traction machine and the internal combustion engine, the internal combustion engine is cranked over and is subsequently accelerated by way of combustion of fuel, and, as soon as the internal combustion engine runs synchronously with the electric traction machine, the internal combustion engine is connected to the drive train.

20. The method according to claim 11, wherein: the adapted characteristic diagram and the resulting shift points are determined multiple times.

21. An automatic transmission for a hybrid vehicle which is configured to be operated in a method according to claim 11.

22. A hybrid vehicle, with an automatic transmission according to claim 21, an internal combustion engine, and an electric traction machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 shows a diagram for a shifting logic for an automatic transmission of a hybrid vehicle, with an adapted characteristic diagram which comprises respective curves for each gear of the automatic transmission, a wheel torque being plotted against a transmission output speed in the respective curves, and the shifting logic for the automatic transmission being predefined on the basis of the diagram, in which shifting logic respective shift points for shifting the automatic transmission at points of intersection of the curves of adjacent gears of the adapted characteristic diagram are fixed.

[0021] FIG. 2 shows a detail of the characteristic diagram according to FIG. 1, a maximum power output of the electric traction machine at a transition speed of the first gear and a maximum power output of the electric traction machine at a transition speed of the second gear, a power-optimum shift point and a maximum power output of the electric traction machine at the optimum shift point, without cranking-over starting being provided being marked.

[0022] FIG. 3 shows a diagram, in which a power output of the electric traction machine is shown plotted against a transmission input speed, a maximum power output for a driver's request of the electric traction machine being available at a transition speed.

[0023] FIG. 4 shows a diagrammatic graph, in which a transmission input torque is plotted against a transmission input speed, a shifting operation being shown jointly in FIGS. 3 and 4.

[0024] FIGS. 5a-d show the characteristic diagram for different power outputs which are available as a maximum for driving the electric traction machine, it being possible to see that the lower the electric power output which is available for the electric traction machine, the further the respective curves of the characteristic diagram shift toward smaller transition output speeds.

[0025] FIGS. 6a-d show a characteristic diagram which is produced for a power output of 130 KW which is available as a maximum for the electric traction machine, and respective characteristic diagrams which are adapted in a manner which is dependent on drag torques which are to be provided for driving an internal combustion engine, it being possible to see that the greater the drag torque which is to be provided, the more the respective curves of the characteristic diagram shift toward smaller wheel torques.

[0026] Identical and functionally identical elements are provided with identical designations in the figures.

DETAILED DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 shows an adapted characteristic diagram 10, on the basis of which a shifting logic for an automatic transmission of a hybrid vehicle can be predefined. This hybrid vehicle is configured, in particular, as what is known as a parallel hybrid, and has both an electric traction machine and an internal combustion engine. The electric traction machine is configured to provide a traction power output for the hybrid vehicle and to crank over the internal combustion engine. In order to ensure potential cranking over of the internal combustion engine via the electric traction machine, a drag torque 18 is provided at the electric traction machine. This drag torque 18 is required for potential cranking over of the internal combustion engine. The drag torque 18 which is to be provided is dependent on: a cut-off position of a piston of the internal combustion engine; a temperature of the internal combustion engine; and, a variable of the internal combustion engine. For a switchover between the electric traction machine and the internal combustion engine, it is provided that the internal combustion engine is cranked over via the electric traction machine and subsequently accelerates independently and therefore by way of combustion of fuel. As soon as the internal combustion engine runs synchronously with the electric traction machine, the internal combustion engine can be connected to the drive train via a clutch. Here, depending on the drive architecture/concept, the electric traction machine can be disconnected from the drive train via this clutch.

[0028] The adapted characteristic diagram 10 which is shown in FIG. 1 comprises a plurality of curves 12, in particular one curve 12 for each gear of the automatic transmission of the hybrid vehicle. Respective shift points 14 for the automatic transmission are fixed at respective points of intersection of curves 12 of adjacent gears. These shift points 14 are stored in a shifting logic for the automatic transmission, a best possible acceleration profile for shifting of the automatic transmission which is neutral in terms of traction force being predefined by way of these shift points 14. For the illustration of the adapted characteristic diagram 10 in FIG. 1, a wheel torque RM in Newton-meters for the first gear is plotted against a transmission output speed N.sub.AB in revolutions per minute, and against a vehicle speed V.sub.FZG in kilometers per hour. On account of the cranking over of the internal combustion engine via the electric traction machine and without a starting device, there is merely a single shift point 14 for shifting which is neutral in terms of traction force for the automatic transmission, instead of a range for shifting which is neutral in terms of traction force for each shifting operation.

[0029] FIGS. 5a-d and 6a-d show the characteristic diagram 10 for respective different maximum power outputs which are available for the electric traction machine (FIGS. 5a-d), and for different drag torques which are to be provided in the electric traction machine (FIGS. 6a-d). The wheel torque RM is plotted in each case against the transmission output speed N.sub.AB both in the diagrams in FIGS. 5a-d and in the diagrams in FIGS. 6a-d. FIGS. 5a-d show the characteristic diagram 10 for a maximum available electric power output for driving the electric traction machine of 150 kW, of 130 KW, of 110 KW and of 90 KW with the respective curves 12 for the respective gears of the automatic transmission. The maximum available power output for the electric traction machine is dependent on an available power output which is provided by way of a battery of the hybrid vehicle for the electric traction machine. Here, the available power output which is provided by the battery for the electric traction machine is dependent on a charging state of the battery and a temperature of the battery. Furthermore, as an alternative, or in addition, the available power output which is provided by the battery can be dependent on its peak power output and/or wiring protection.

[0030] It can be seen in FIGS. 5a-d that the respective curves 12 of the characteristic diagram 10 shift toward smaller transmission output speeds in the case of a decreasing maximum available electrical power output for the electric traction machine. In particular, this can be seen by way of respective transition speeds 16 of the respective curves 12. In the case of a transmission output speed N.sub.AB below the transition speed 16 of the respective gear, a power output which can be provided by the electric traction machine is limited by way of a limit torque of the electric traction machine. In the case of transmission output speeds N.sub.AB which are greater than the respective transition speed 16 of the respective gear, the power output which can be provided by the electric traction machine is constant without the provision of cranking-over starting, and is dependent on the transmission output speed when cranking-over starting is provided. Up to the respective transition speed 16, the wheel torque is approximately constant, and a power output which the electric machine can provide for the hybrid vehicle as traction power output rises up to the transition speed 16, at which a maximum traction power output for the hybrid vehicle is provided by the electric traction machine. In particular, the traction power output rises in a linear manner until the transition speed 16 is reached. In the case of a transmission output speed above the transition speed 16, the wheel torque decreases, and the traction power output which is provided by the electric traction machine for the hybrid vehicle increases in a linear manner on account of the power output provision for cranking-over starting of the internal combustion engine. In particular, the power output provision for cranking-over starting of the internal combustion engine increases in a linear manner as the transmission input speed increases.

[0031] The lower the maximum available electrical power output which is provided for the electric traction machine, the lower the transition speed 16. The range, in which a maximum power output prevails in a gear, shifts toward smaller speeds and decreases. This results in different gears for an identical speed in a manner which is dependent on the maximum available electrical power output for the electric traction machine.

[0032] FIGS. 6a-d show the characteristic diagram 10 for different provisions of drag torque, in particular, for a provision of drag torque of 0 Newton-meters, of 50 Newton-meters, of 100 Newton-meters, and of 150 Newton-meters. As can be seen particularly well in FIGS. 6a-d, there is a range for shifting of the automatic transmission which is neutral in terms of traction force in respective adjacent gears for a provision of drag torque of 0 Newton-meters. The higher the drag torque 18 which is to be provided, the further the respective curves 12 of the characteristic diagram 10 shift toward smaller torques, in particular wheel torques RM. As can be seen in FIGS. 6a-d, the respective curves 12 of the characteristic diagram 10 are shifted with an increasing drag torque 18 to be provided, in such a way that the respective wheel torques, which are available for driving, of the respective curves 12 are shifted downward. Here, the respective transition speeds 16 remain identical, a target speed and therefore the respective shift point 14 decreasing with an increasing drag torque 18 to be provided. In the case of transmission output speeds N.sub.AB which are greater than the respective transition speed 16 of the respective gear with a provision of drag torque, the power output which can be provided by the electric traction machine is dependent on the transmission input speed. Therefore, the power output for driving reduces while the provision of power output for cranking-over starting rises. A sum of the power output available for driving and the provision of the power output remains identical, however, for example, 130 kW.

[0033] For the determination of the characteristic diagram 10, therefore, the maximum available electrical power output for driving the electric traction machine is determined, and the characteristic diagram is produced, in a manner which is dependent on this determined maximum available electrical power output for the electric traction machine. This characteristic diagram is adapted in a manner which is dependent on the drag torque 18 to be provided, by each curve 12 being reduced by the drag torque 18 to be provided. Subsequently, the shifting logic is predefined, in which respective shift points 14 for shifting the automatic transmission are fixed at points of intersection of the curves 12 of adjacent gears of the adapted characteristic diagram 10. For shifting of the automatic transmission which is neutral in terms of traction force, the automatic transmission is shifted at the respective shift points 14 using the shifting logic. In particular, the automatic transmission is shifted on the basis of the transmission output speed N.sub.AB.

[0034] Since an electrical power output which is available for the electric traction machine can change during a journey of the hybrid vehicle (in particular, on account of a protective function of the battery, and/or a strategic power output reduction of the battery, in particular in order to avoid excessively rapid ageing of a high voltage store of the battery, or for component protection), and the drag torque 18 to be provided can additionally change during the journey of the hybrid vehicle (in particular, on account of the temperature change of the internal combustion engine and/or a change in a cut-off position of the piston of the internal combustion engine), it can be provided that a method for operating the automatic transmission of the hybrid vehicle (in the case of which method the characteristic diagram 10 is produced and adapted and the switching logic is subsequently predefined), is carried out during a journey of the hybrid vehicle. In particular, the adapted characteristic diagram 10 and the resulting shift points 14 are determined multiple times and therefore repeatedly, in particular at regular time intervals, in order to make shifting of the automatic transmission which is particularly neutral in terms of traction force possible at any time.

[0035] In the following text, a calculation of a target speed with a provision of torque for cranking-over starting will be explained by way of example, the respective points being shown in the graph in FIG. 2, in which the wheel torque RM in Newton-meters for the first gear is plotted against the transmission output speed N.sub.AB in revolutions per minute, and against the vehicle speed V.sub.FZG in kilometers per hour.

p.sub.Max,G1=maximum power output at the transition speed from the first gear
p.sub.Max,G2=maximum power output at the transition speed from the second gear
p.sub.Opt=optimum (power output) shift point
P.sub.Max=max. power output at the optimum shift point (without provision of cranking-over starting)
P.sub.Schlepp=provision of power output for cranking-over starting

[00001]$\begin{array}{cc}{P}_{\mathrm{Opt}}=P_{\mathrm{Max}}-P_{\mathrm{Schleppstart}}& \left(i\right)\end{array}$$\begin{array}{cc}{P}_{\mathrm{Max},G1}=m_{\mathrm{Eck}\text{?}G1}.Math.\frac{n_{\mathrm{Eck}\text{?}G1}}{9550}& \left(\mathrm{ii}\right)\end{array}$$\begin{array}{cc}{P}_{\mathrm{Schlepp}}=m_{\mathrm{Schlepp}}.Math.\frac{n_{\mathrm{opt}}-n_{\mathrm{Eck}\text{?}G1}}{9550}& \left(\mathrm{iii}\right)\end{array}$$\begin{array}{cc}{m}_{\mathrm{Opt}}=\frac{m_{\mathrm{Eck}\text{?}G1}}{i_{\mathrm{Gang}}}& \left(\mathrm{iv}\right)\end{array}$$\begin{array}{cc}{P}_{\mathrm{Opt}}=m_{\mathrm{opt}}.Math.\frac{n_{\mathrm{opt}}}{9550}& \left(v\right)\end{array}$$\begin{array}{cc}{P}_{\mathrm{Max},G1}=P_{\mathrm{Max}}=P_{\mathrm{Max},G2}& \left(\mathrm{vi}\right)\end{array}$$P_{\mathrm{Opt}}=P_{\mathrm{Max}}=P_{\mathrm{Schleppstart}}{m}_{\mathrm{Opt}}.Math.n_{\mathrm{Opt}}=m_{\mathrm{Eck}\text{?}G1}.Math.n_{\mathrm{Eck}\text{?}G1}-m_{\mathrm{Schlepp}}.Math.\left(n_{\mathrm{Opt}}-n_{\mathrm{Eck}\text{?}G1}\right)$$\frac{m_{\mathrm{Eck}\text{?}G1}}{i_{\mathrm{Gang}}}.Math.n_{\mathrm{Opt}}=m_{\mathrm{Eck}\text{?}G1}.Math.n_{\mathrm{Eck}\text{?}G1}-m_{\mathrm{Schlepp}}.Math.n_{\mathrm{Opt}}+m_{\mathrm{Schlepp}}.Math.n_{\mathrm{Eck}\text{?}G1}\left(\frac{m_{\mathrm{Eck}\text{?}G1}}{i_{\mathrm{Gang}}}+m_{\mathrm{Schlepp}}\right).Math.n_{\mathrm{Opt}}=\left(m_{\mathrm{Eck}\text{?}G1}+m_{\mathrm{Schlepp}}\right).Math.n_{\mathrm{Eck}\text{?}G1}$$n_{\mathrm{Opt}}=\frac{\left(m_{\mathrm{Eck}\text{?}G1}+m_{\mathrm{Schlepp}}\right).Math.n_{\mathrm{Eck}\text{?}G1}}{\frac{m_{\mathrm{Eck}\text{?}G1}}{i_{\mathrm{Gang}}}+m_{\mathrm{Schlepp}}}$$\text{?}\text{indicates text missing or illegible when filed}$

[0036] Example for 130 kW available power output (all torques and speeds relate to the first gear):

[00002]$n_{\mathrm{Eck}\text{?}G1}=2759\mathrm{rpm}{m}_{\mathrm{Schlepp}}=100\mathrm{Nm}{m}_{\mathrm{Eck}\text{?}G1}=350\mathrm{Nm}{n}_{\mathrm{Opt}}=\frac{\left(350\mathrm{Nm}+100\mathrm{Nm}\right).Math.2759\mathrm{rpm}}{\frac{350\mathrm{Nm}}{1,562}+100\mathrm{Nm}}=3831\mathrm{rpm}$$\text{?}\text{indicates text missing or illegible when filed}$

[0037] FIG. 1 shows a first situation S1, in which an excessively early upshift is shown. Furthermore, FIG. 1 shows a second situation S2, in which an excessively late upshift is shown. This excessively late upshift in the second situation S2 and the excessively early upshift in the first situation S1 are in contrast to the shift of the automatic transmission which is neutral in terms of traction force and is predefined by the ideal shift points 14.

[0038] FIGS. 3 and 4 show a shifting operation from a first gear into a second gear of the automatic transmission. Here, a power output P is plotted against a transmission input speed N.sub.E in FIG. 3. In FIG. 4, for a limit torque of 450 Newton-meters and a maximum electrical power output of 130 KW which is available for the electric traction machine at a provision of drag torque of 100 Newton-meters, a transmission input torque GM in Newton-meters is plotted against the transmission input speed NE. This results in a torque of 350 Newton-meters which remains for the driver's request, which in turn results in a maximum power output of 101 kW at the transition speed 16.

[0039] Different ranges result in FIG. 3. A first (power output) range B1 cannot be moved to on account of a torque limitation of the electric traction machine. The electric traction machine can make a power output provided by the battery available only from the transition speed 16. A second range B2 describes the provision of power output of the electric traction machine for cranking over the internal combustion engine, the provision of power output increasing in a linear manner with a rising rotational speed. The power output which can be moved to is shown for the hybrid vehicle in a third range B3. This power output which can be moved to is limited by a maximum power output release 20. As can be seen in the third range B3, a maximum power output for a driver request prevails at the transition speed 16.

[0040] FIGS. 3 and 4 show the shifting operation of the automatic transmission from the first gear into the second gear, the automatic transmission being set in the first gear in a first step 1, and the transmission input speed being increased as far as the transition speed 16. Here, a power output which can be utilized for acceleration is limited by a maximum torque which can be provided by the electric traction machine, in the present case 350 Newton-meters. In a second step 2 of the method, the transmission input speed corresponds to the transition speed 16, as a result of which the power output which is available for acceleration corresponds to a power output optimum. The transmission input speed is subsequently increased further until, in a third step 3, the automatic transmission is shifted from the first gear into the second gear. In a fourth step 4 of the method, the second gear is engaged in the automatic transmission, a power output which can be utilized in the current and in the next higher gear, in the present case the first gear and the second gear, being identical in the third step 3 and in the fourth step 4. In particular, in the third step 3, the automatic transmission is shifted at one of the predefined shift points 14 of the shifting logic. If this shift point 14 is exceeded, the power output which is available for driving undershoots the power output in the next higher gear. This is due to the fact that the provision of power output at the higher transmission input speed is higher than the power output deficit on account of the torque limitation in the present case to 350 Newton-meters in the next higher gear. In the fourth step 4, the rotational speed at the transmission input is subsequently increased further until, in the fifth step 5, the transition speed 16 for the second gear is reached. In the case of this transition speed 16, the maximum power output of the electric traction machine is available for the second gear as traction power output for the hybrid vehicle. For each further shift of the automatic transmission, the sequence is repeated in accordance with the same principle. In the case of a shift of the automatic transmission, the respective gears are fully utilized such that the following speed in the next gear corresponds to the transition speed 16 and/or lies slightly below the transition speed 16 in a manner which is dependent on the cranking-over power output to be provided, as can be seen in the figures in step 4.

[0041] Overall, the disclosure shows how a calculation of optimum-power shift points 14 can take place in the electric method with consideration of the provision of power output for cranking-over starting.

LIST OF DESIGNATIONS

[0042] 10 Characteristic diagram [0043] 12 Curve [0044] 14 Shift point [0045] 16 Transition speed [0046] 18 Drag torque [0047] 20 Maximum power output release [0048] B1 to B3 Respective ranges [0049] 1 to 5 Respective steps of a method [0050] S1, S2 Respective situations [0051] RM Wheel torque [0052] N.sub.AB Transmission output speed [0053] V.sub.FZG Vehicle speed [0054] GM Transmission input torque [0055] N.sub.E Transmission input speed [0056] P Power output